Sheet metal lock



July 5, 1932. E; 4FQRBES; 1,866,156`

SIHEET METAL Lock Filed Nov@ 2 19:51

cludes a socket having a cylindrical wall 12, a

Patented' July 5, 19.32

I UNITED p, STATES rnrlzu'r- I OFFICE ammalaA r. romans, or noacnnsrnn,MASSACHUSETTS, AssxeNon or 01m-mem 'ro WILLIAM n. McxaNNEYnND cnn-ummmTo ALMA n. Mmmm, :com or raunron, MASSACHUSETTS' SHEET METAL LOCKApplication mea november a; 1931. serial no. 572,594.

This invention relates chiefly' to a lock ada ted to secure the `iap ofan envelope to the ack thereof in such manner'that the iap cannot beseparated from the back without I mutilating the lock and therebyindicating that the envelope has been opened.

. The object is to provide a simple and effective lock of compact formand composed entirely of two sheet metal parts or members 10 oneconstituting a socket and the other a stud, each made from a singlepieceof sheet metal;

Of the accompanying drawing forming a part of this specification-,

Figures 1 and 2 show in perspective the l5 parts or members of myimproved lock separated from each other, substantially the preferredsize of said 'members being shown by these figures.

Figure 3 shows the lock in section on a 20 larger scale.

Figure 4 is an Figure 3.

The same reference characters'indicate the same parts in all of thefigures.

One of the two members of the lock in enlargement of a portion of headclosing one end of the wall, an-inwardly proectin annular rib 14contracting the opposite en of the wall, and a base flange 15 rovidedwith attaching means, all formed rom a single piece ofv sheet metal.VThe rib 14 is a folded zone of the socket wall as best shown by Figure4.

The other member is a vstud having a hollow cylindrical wall 16, a head'17 closing an end of said wall, and a base flange 18`having attachingmeans, all formed from a single pieceof sheet metal.

The stud wall 16 is cut to define a plurality of integral outwardlyinclined resilient struts 19 preferably three 1n number, joined at theinner ends to the head 17. Y

The stud is formed to enter the socket and the -struts 19 are adapted tobe sprung inwardlyby' the rib during the insertion of the stud into thesocket until their free'ends pass across the rib 14, and then to springoutwardly so that their outer ends engage the rib 14, and also engage orbear on the-inner surface of the socket wall 12 as shown by Figure 3.The struts are thus caused to lock the socket to the stud at a.plurality of oints, the struts being covered and guarded y the socket sothat they cannot be Ydisengaged from the rib without mutilation.

The base flanges 15 and 18 may be provided withintegral means wherebythey are adapted to be attached respectively to the flap 21 and back 22of an envelope, said means being preferably embodied in spurs 23 formedon the flange 15, and spurs 24 formed on the flange 18.

It will be seen that the forms shown by the drawing may be imparted by'automatic means to sheet metal blanks, the blank'for the socketincluding metal for the wall 12,.the head 13, the annular rib 14, andthe spurs 20, while the blank for the stud includes metal for the wall-16, the head 17, the struts 19 and the spurs 24.

When the lock is intended for use on an en- 70 velope the preferredheight of the socket wall 12 is about three thirty seconds of an inch,Yso that the socket head does not project objectionally from an envelopeto which the socket is attached. This minimum projection is feasiblebecause of the sheet metal construction. The sheet metal ofthe memberwhich includes the stud is preferably sheet steel to provide suitablyresilient struts. The sheet metal of the member which includes thesocket is not necessarily of high resilience, Y

` and is preferably rustless metal such as sheet brass. This metal isadapted to have an ornamental finish and is suiciently ductile to foldedrib to be formed without enable the cracking the metal.

It is obvious that the use of the described, lock is not necessarilylimited to envelopes.

I claim:

1 A lock of thelcharacter stated composed of two members each madewholly from asingle piece of sheet metal, one member in cluding a sockethaving a c lindrical wall, a head closing one end of t e wall, Aan in-'Wardly projecting annular rib contracting the opposite end of the wall,and a base flange surrounding the rib and having attaching means, theother member including a stud 'havin a cylindrical wall, a head closingone end o the wall', resilient struts incline out- 10 wardly from thewall, and a base iange surroundmg the opposite end of the the wall andhaving attaching means, the stud and struts being insertable through therib into the socket, and the struts belng adapted to spring I' d outward1nto engagement with the rib at, a

plurality of points, each strut bein joined. at its inner end to thestud head and earing at its opposite end on the socket wall so that theen agement of the struts with the rib and 1 soc et wall so connect thestud with the socket that said parts are inseparable without mutilation.l

2. A lock as specified by claim 1, the said 'b being a folded zone ofthe socket wall.

3.l A lock as specified by claim 1, the sheet metal of the member whichincludes the stud being relatively resilient, and the sheet metal ofthe/member which includes the socket be- 0 ing relatively ductilerustless, and adapted to have an ornamental sh.

, In testimony whereof I have aixed my signature.

EDWARD P. FORBES.

